Switch-operating mechanism



July 2l, V1925.

c.; CANFIELD SWITCH OPERATING MECHANIS'M Filed May 41'7. 1923 Patented July 2l, 1925.

UNITED STATES PATENT OFFICE.

CHARLES E. CANFIELD, 0F IPITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION 0F NEW YORK.

SWITCH-OPERATING MECHANISM.

Application led May 17, 1923.

To all Iwhom it may concern.'

Be it known tnat l, CHARLES E. CiiNrmr-D, a citizen of the United States, residing at Pittsfield, county of Berkshire, State of Massachusetts, have invented certain new and useful Improvements in Switch-Operating Mechanisms, of vwhich the following is a specification.

My invention relates to switch operating mechanism and is particularly applicable in connection with a ratio adjusting switch for an oil immersed transformer where. the switch is immersed with the transformer in the same body'of oil within a common casing. F or the convenient operation of this type of switch, it is cust-omary to extend an operating handle or rod from the switch through the casing wall to some accessible point outside the transformer and switch casing. The general object of the invention is to provide acombined switch operating handle or rod and transformer bushing so that the necessity for an extra opening in the casing wall for the switch operating handle is avoided.

The casing of an oil immersed transformer is often completelyT filled with oil in communication with a separate partially filled expansion chamber to accommodate the expans'ion and contraction of the oil due to variations in temperature. The oil level in the expansion chamber is usually somewhat higher than the top of the oil in the transformer casing so that the oil in the casing is under a pressure slightly greater than that of the surrounding air. This prevents air with its oxygen and possibly some moisture being dra-wn into the casing to form explosive mixtures with the oil vapor in case of an accidental leak in the casing. Under such conditions as these, the invention is of advantage in that the switch operating handle may be brought out at the upper end of a transformer bushing above the level of the oil in the expansion chamber and therefore at a point where there can be no leakage of oil through joints or connections which may not be perfectly oil tight.

Other advantages will be apparent from the following description taken in connection with the accompanying drawing which shows one embodiment of the invention and in which Fig. l is an elevation of a combined switch operating handle and bushing as applied to an oil immersed transformer of the Serial No. 639,658.

conservator type, a portion of the transformer casing being broken away to reveal details, and Fig. 2 is a longitudinal sectional view of a portion of the combined switch handle and bushing.

Like reference characters refer to similar parts in both figures of the. drawing.

The drawing shows one embodiment of the invention as applied in connection with a transformer l immersed in a body of cooling and insulating oil with a casing 2. The casing 2 is completely filled with oil which also extends through a communicating pipe 3 and partially fills an expansion chamber ll, the oil level in this expansion chamber being somewhat above the top of the oil in the casing 2 to create a slight outward pressure in the casing. This prevents any air with its oxygen and moisture being drawn into the casing to form an explosive mixture with the oil vapor in the casing and tov contaminate the oil and impair its insulating properties. The space above the oil in thcI expansion chamber is in communication with the outside air through a small vent 5 to permit the free interchange of oil between the casing 2 and the expansion chamber.

One of the transformer leads 6 is brought out of the casing 2 through high tension bushing 7 which is mounted through an -A L opening in the top of the casing. the lioint about the opening being made oil tight. A. small tap switch 8 for changing the ratio of transformation of the transformer is immersed in the oil beside the transformer and is operable by an operating handle or rod 9. In accordance with the invention, this operating rod 9 extends through and to the upper end of the bushing 7 where means is provided as will be described for turning the rod to operate the switch.

The bushing shown in the drawing is similar to the usual type of oil filled high tension transformer bushing. Fig. 2 shows in longitudinal section the details of the inner and end portions of the bushing, the tubular petticoated outer portion surrounding the oil space being omitted. The switch operating rod 9 is disposed along the axis of the bushing inside a tube l() of good conducting material such as copper, the inner end of this tube 10 being connected by aterminal 11 to the transformer lead 6. A second tube 12 outside the conducting tube 10 affords stiffness and support to the bushing structure. The tube 12 bears at its inner or lower end on the terminal 11 and its'outer er upper end is threaded into an annular meniber 18 provided with hooks or lugs-1li for lifting the bushing. in annular conducting member 15 has a splittubular portion fitting about the conducting tube 10 to which it is clamped by a taper threaded nut 16. A key 17 prevents relative rotation between the annular member'15 and the tube 10 The annular member 15 and the conducting tube 10 are further secured together by a nut 18 threaded onto the tube and down against the member 15. ri cap 19`is pressed down by the nut 2O against the annular member 15, relative rotation between the cap 19 and the switch operating rod 9 being prevented by the key 21. i e annular mein,- ber 15 is provided with an int gral terminal 22 for Connection'to an outside transformer lead. 1t will be seen thata conducting path from the transformer is provi ed through the bushing by way of' the transiornier lead 5, the terminal 11, the conducting tube 10, and the annular member 15 and its terminal 22.

The ratio of transformation of the transformer 1 is determined by the setting of the switch 8 and-this may be changed or varied desired by rotating the switeh operating rod 9 by means of the cap 19, the cap being first released by loosening the nut 20. The

setting of the switch S 'may be indicated byk a pointer 28 on the cap 19 and suitable scale @il on the ri'in of the annular ineinoer Y 15.' The switch is retained in any desired position or setting by tightening the nut 2O against the cap 19. During vthe setting of the switch the transformer should of course a n 7 7 be disconnected Ironi any source f current to avoid danO'er to the operator.

m 2D Y n 1 lhe expansion chamber t is prererabiy so located that the level of the oil therein is above the top of the oil in the transformer :terasse asing 2 but below the upper ends of the tubes 10and 12. This avoids the necessity of any external joints along the switch operating rod il below the highest oil level and there can therefore be no leakage of oil past this rod from within the transformer casing. rlhe extension of the switch operating 'ie-ans through the bushing struct is of further advantage in that no extra opening in the transformer casing is required. Y

Virhat l claim new by Letters Patent of isf* 4nrlhe eombiii'ation with easing enclosinrf'a transformer, of an expansion chamber iiiieating with said casing, a body of insulating liquid filling said casing and partially filling said expansion chamber, the level of said liquidv within the expansion chamber being above the top of the liquid within the casing, a transformer tap changing switch immersed in the liquid within said casing, and a high tension bushing extending through an opening in said casing and enclosing a switch operating means and high tension lead from said transformer, the switch operating Vmeans extending through said bushing to a point above the level of the liquid. in said expansion chamber. y

2. The combination in a high tension insulating bushing structure for electricalapparatns, of an external tubular insulating portion, a terminal at each end of said insulating portion, a tubularconductor eXtendand desire to secure the United States,

ing through said insulating portion and connecting said terminals7 and a switch operating rod extending through Vsaid tubular conductor. p

n witness whereof, l have hereunto set my hand this 15th day of May, 19;3.

' onrinnns n. oiiiirmrn. i 

